We are in the process of synthesizing specific glycolipids that are structural analogs of mycolyl acetyl trehalose from Mycobacterium tuberculosis. Each glycolipid will be tested in combination with purified endotoxin components from the Re mutant of Salmonella typhimurium for antitumor activity in several animal tumor systems. We wish to find the simplest combination that exhibits the highest antitumor activity. We are developing a suitable murine tumor assay system using leukemia P-388, L-1210, B-16, and Madison 109 lung carcinoma. We have purified the endotoxin to a high state of purity using DEAE-cellulose and Sephadex LH-20 columns. The endotoxin from the former column was inactive in tumor regression assay using the guinea pig system, whereas the endotoxin from the latter column was very active. We are now able to fractionate the mycolic acids on the preparative scale. These purified acids will be used to synthesize the glycolipids. We have modified published procedures for the organic synthesis of trehalose monomycolates to achieve high yields. We shall continue our work on improving the yields in the organic synthesis of the glycolipids and further fractionate the endotoxin and test for biological activities. We shall continue developing murine tumor assay systems and rapid in vitro assay systems that are suitable for immunotherapeutic agents.